This invention particularly relates to systems which are effective in detecting and communicating data about operating conditions of electronic apparatus such as aircraft navigational aid transmitters.
This invention is an improvement upon a REMOTE OPERATING CONDITION DATA ACQUISITION SYSTEM invented by Donald J. Toman which forms the subject matter of U.S. Pat. No. 3,820,074 issued June 25, 1974, and assigned to the same assignee as the present application.
One of the basic purposes of such a system is to obtain operating information and data relating to an electronic apparatus such as a navigation aid transmitter on a periodic basis. The data is preferably stored at a local station near the transmitter and then later sent to a central station for processing in response to a request signal from the central station. Ideally, the local station includes a capability of calling in to the central station whenever there are emergency "alarm" conditions of the electronic apparatus.
It is one important object of the present invention to provide an improved operating condition data communication system which is characterized by extreme simplicity and reliability at a minimum cost. The system is particularly characterized by a minimum equipment cost at the local station, preserving as many functions as possible for the central station which can serve many local stations.
As mentioned above, a data commmunication system of the above description preferably provides the capability of answering commands from the central station to transmit information, and also includes the capability of locally initiating calls to the central station under alarm conditions. This necessarily requires at least two different modes of operation and implies two completely different and independent sets of signal processing equipment, one for receiving incoming calls and commands, and one for transmitting calls and communications.
It is another important object of the present invention to provide important economies, especially in the local station, by combining as much as possible the signal processing apparatus used for communications initiated from the central station and communication initiated at the local station.
The local station in an operating condition data communication system of the above description necessarily requires logic circuitry which is capable of dealing with operating commands by carrying out logical programs, including safeguards to assure the completion of such commands, and a capability for resetting the logic circuits whenever the commands cannot be carried out, or are not completed.
It is another important object of the present invention to provide a local station in which the simplest possible provisions are made for assuring that if commands are not carried out, the signal processing circuits are reset so that additional attempts can be made to carry out the commands.
Aircraft navigational aid transmitters are often installed in groups. For instance, if the apparatus is for an instrument landing system, there may typically be a localizer transmitter for the purpose of transmitting azimuth guidance signals, a glide slope transmitter for the purpose of transmitting glide slope guidance signals, and at least one marker beacon transmitter, characterized as a "middle" marker, for the purpose of transmitting a very narrow vertical radio beam to signal the guided aircraft at the point in the landing approach where the pilot usually should decide whether to abort or complete the landing. These transmitters are preferably physically separated. Preferably, data should be accumulated with respect to each of these transmitters, and alarm conditions in any one of the transmitters should result in a call-out to the central station.
Accordingly, it is another object of the present invention to provide an improved operating condition data communication system for serving a related group of transmitters and which includes one or more satellite local stations which are capable of communicating with a central station through equipment which may be used in common with a main local station.
Other objects and advantages of the invention will be apparent from the following description and the accompanying drawings.